How Do Gravity, Balance & Leverage Factor into Mobile Crane Stability
Tipping accidents are among the most common types of incidents reported by crane operators, especially those who lift heavy loads via mobile cranes. The engineering technology behind crane manufacturing highly relies on key factors, such as gravity, leverage, and balance.
Let’s put it this way: a crane uses leverage to remain in balance while lifting heavyweights. When a crane’s upper-work, including the load, counterweight, boom, or cab rotates, it changes or fluctuates the fulcrum, the leverage point, and the center of gravity’s location.
The G Forces
We’re well-versed with Einstein and Newton's gravitation concept fairly enough to understand that it's responsible for making objects drop on the ground. The point where the weight of the load is evenly distributed is known as the center of gravity. Calculating the center of gravity of the load is a crucial step in material handling.
The beam, which is balanced on the hinge, remains in balance until the leverage on one side of the fulcrum is equivalent to the opposite side. If either of the objects placed on the beam weighs more than the other, the beam will tip, often in the heavier load direction.
The only way to resolve the issue at hand is to move the fulcrum a little closer to the heavier load. When the fulcrum is pushed, it helps the beam retain balance, allowing each object to counterbalance the other.
Counterbalancing is highly dependent on the object’s leverage being equal. Here’s how to calculate the leverage.
Multiply the crane's weight by the distance from the CG to the tipping point, and then calculate the distance of the object being lifted from the fulcrum. For example, if the weight of the object is 300 pounds, multiplying it by a distance of the load (Let's presume a 5 feet distance from the fulcrum) results in a weight that equals 1500 pounds.
For the other side, the 100-pound weight, when multiplied by the 15 feet distance from the fulcrum, also results in 1500 pounds, making both sides of the equation equal. This means the beam will remain balanced as the leverage derived on both sides of the fulcrum is the same.
Balance or ‘Stability”
After understanding precisely how stability is achieved, it’s important to factor in the variables that influence balance, such as radius changes, load changes, and more.
While this example helped achieve an ideal 'balance,' it's vital to remember that in practical settings, as soon as a heavier load is picked up on either side, the personnel must compensate by increasing the leverage on the other side of the beam.
Similarly, when a lighter load is picked up, compensate by decreasing the leverage on the opposite side of the beam.
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